Selective production of cycloalkanes through the catalytic hydrodeoxygenation of lignin with CoNi@BTC catalysts without external hydrogen.

Depolymerizing lignin to produce high-value chemicals under mild conditions is a significant way to achieve the sustainable development of agriculture and forestry industry, and attracting a growing number of attentions. In this work, a bimetallic Ni-Co catalyst (CoNi@BTC) was prepared by using MOF as precursor and then employed to degrade the lignin model compounds and real corncob lignin. The resulted CoNi@BTC mainly composed of Co, Ni, Co and Ni oxides. Compared to the pure Co@BTC and Ni@BTC, CoNi@BTC exhibited much better (4.0-4.75 times) performance on cracking the ether bonds without H. During the degradation of lignin model compounds, CoNi@BTC could not only completely crack the various ether bonds (α-O-4, β-O-4 and 4-O-5), but also further hydrogenate the intermediates, resulting the highly selective yield of cycloparaffin (>79.58 %) and cyclohexanol (100 %). The mechanism on ether bond cleavage was ascribed into the weakly acidic site originating from Co and the strongly acidic site stemming from Ni, while the further hydrogenation was attributed into the strong activity of Ni on activating H. Due to the synergistic effect of Ni and Co, CoNi@BTC also exhibited full depolymerization of real corncob lignin and achieved the high selectivity of cycloparaffin (80.16 %) in the bio-oil. This work will provide a new strategy to the resource utilization of the biomass waste.